# Is Max Planck law true for all electromagnetic waves?

1. Dec 23, 2013

### wolvekampp

Is it true that the energy in electromagnetic waves can only be released in "packets" of energy?

Or is this only the case for a system where a standing wave change from one mode to another which results in sending out an electromagnetic wave (photon).

In other words if I ride on my bike and connect my dynamo to an electronic circuit to send out low frequency low energy electromagnetic waves (RF radiation) do I have to ride 1 meter extra to create the discrete energy needed for the packet (E=hf)?

If it isnâ€™t true is a photon a special kind of electromagnetic radiation where properties are directly related with the change in the system which created the photon.

2. Dec 23, 2013

### bhobba

Yes - that's true.

But the correct explanation is Quantum Electrodynamics - QED for short - not the adhoc hypothesis of Plank or even Einstein.

I have zero idea what you mean.

However QED is a Quantum Field Theory and incorporates relativity from the outset.

Thanks
Bill

Last edited: Dec 23, 2013
3. Dec 23, 2013

### wolvekampp

Bill, thanks for your reply. Sadly I didn't find the answer in QED but I learned something new :). What I mean with the bike story is: There is a discrete nature in the way a photon is created when an electron that is bound to an atom move from a higher energylevel to a lower one. I do not see the discrete nature in a radio transmitter. That is why I ask the question. Is there a way to explain the discrete nature of light (electromagnetic waves can only be released in "packets" of energy) if you look at the operation of a radio transmitter.

4. Dec 23, 2013

### Bill_K

There are many other ways in which a photon may be created. Not all light comes from spectral lines. Any time a free electron is accelerated, it radiates electromagnetic waves.

5. Dec 23, 2013

### bhobba

Scratching my head about that. Quantized fields explain exactly why photons exist eg the creation and annihilation operators.

Yes - the creation and annihilation operators of the quantisized EM field:
http://en.wikipedia.org/wiki/Quantization_of_the_electromagnetic_field

See the section of Fock states.

Thanks
Bill